Attorney General Mark Herring says Dominion Virginia Power should drop plans to build a third reactor at the North Anna nuclear plant. Dominion has not committed to building the additional reactor, but the utility says it’s on pace to spend nearly $2 billion on the potential power source by the end of 2018.

The Richmond Times-Dispatch reports an expert witness for the attorney general’s office estimated the cost of adding a third reactor at North Anna would top $19 billion and increase customers’ bills by 25%. Dominion executives say they expect a federal license in 2017. They say halting work on the design would be premature.

Nuclear power accounts for more than 40% of Dominion’s output.